Foundation and early survival of Atta sexdens rubropilosa (Hymenoptera: Formicidae) colonies in contrasting environments

Leaf-cutting ant queens of the genus Atta (Hymenoptera: Formicidae) leave mature nests during nuptial flights to establish new colonies, but the factors influencing patterns of colony foundation remain poorly understood. This study describes foundation and evaluates early colony survival of Atta sexdens rubropilosa under contrasting environmental conditions. The research was conducted in Botucatu, São Paulo state, Brazil, in two 700 m² areas: (A) an open, sun-exposed, urban site with bare soil, and (B) a shaded area near a river, with riparian vegetation and native trees. Nine hundred and six queens were recorded founding nests, 556 (61.4%) in the open area and 350 (38.6%) in the shaded area, during the nuptial flight in November 2024, resulting in 0.794 and 0.500 queens/m², respectively. After four months, the survival of 300 marked nests in each area was evaluated. Thirty and 135 nests remained active in the open (0.043 nests/m²) and shaded (0.193 nests/m²) sites, respectively (p < 0.001). These results indicate that colony foundations were not evenly distributed between the two environments and that early survival differed markedly between them. Because the study is observational and based on two non-replicated sites, the findings should be interpreted as descriptive evidence of habitat-associated differences rather than definitive proof of active habitat selection.